One possible solution is to use a global phrase replacement application like Phrase Express, which you can limit specific phrase 'shortcuts' to a specific application, like Mathematica.  I store many shortcuts in Phrase Express for Mathematica, which helps speed up my input dramatically, and I don't need to worry about using packages or default notebooks to do the same thing.

Phrase Express is a closed source application, which offers a free version with limited functionality, and a paid version for more advanced functionality.